Method of and means for demonstrating and visualizing the track of alpha rays



. C. T. KNlPP METHOD OF AND MEANS FOR DEMONSTRATING AND VISUALIZING THE TRACK OF ALPHA RAYS Filed Dec. 19, 1924 Feb. 15,1927. 1,617,397

,tion, a simple mode of operation and simple Patented Feb. '15, 1927.

UNITED STATES v v 1,617,397 PATEN oFFIjc-E.

CHARLES T. KNIPP, OF UBBANA, ILLINOIS.

' METHOD or AND MEANS. ron DEMONSTRATING'AND vIsuALizrne THE TRACK or ALPHAJRAYS.

Application filed December 19, 1924. II Serial No, 757,081.

My invention relates to a method of and means for demonstrating and visualizing the I track of alpha rays.

About fifteen years ago Mr. C, T: .R. \Vilson of Cambridge, England, constructed a so-called Cloud apparatus for making visible the traces or tracks o f alpha particles thrown ofi from radio active materials. His device operated as follows Dust free air saturated with water vapor was suddenly expanded at the same instant that alpha ray particles were allowed to pass through it. The ions, formed along the path of a particular particle, acted as little centers or nuclei of condensation for mo sture,

which grew. rapidly into droplets and became visible under a strongbeain of light. The pathof a particle thuswas made visible as a streak ofilluminated dropletsof vapor The apparatus required, heretofore has been complicated, expensive, and diiiicult to maintain in operative condition. I I I I provide, according to the present invenapparatus for producing the conditions necessary to make such rays visible. I I I I II In the preferred form of my invention, I provide a glass containing vessel blown into the form of a pyrex beaker inverted and having a lateral opening in which there is seated a source of alpha rays. This takes the form of a small plug of aluminum seated in the lateral opening, the plug having at itsinner end a tiny source of alpha rays as, for example, bromide ofradium, seated in a protected cavity in the plug.

To the main opening or neck of the glass bottle or inverted beaker I attach abattery syringe bulb of india rubber. v'Ihevessel and bulb are then filled with liquid to within substantially an inch or .so of the closed top. An electrode is mounted in the closed top and another electrode is connected with the liquid, which liquid -is slightly acidulated water to make'it conductive so that in effect it becomes the lower electrode. A source of current, of say from 100 to 200 volts direct current, is connected to said electrodes for establishing an. electrostatic field in the region where the alpha par ticles move. The'purpose'of this field is to sweep the space between said plates or Ielectrodes free ofions between successive operations or demonstrations.

To assist in making the'track Vi s ible, :I

provide a lantern or projector and arrange to throw a strong beam oflight into the space between the plates, 1

To operate the ap'paratus,.tl1e hand bulb of the syringe is squeezed to produce a pressure in the cavity or field between the. plates which cavity or field is filled with air and water vapor. Then' the bulb is quickly releasediand! just I at the instant when the proper conditions of expansion prevail, the

tracks of the alpha particles appear plainly as smallstreaksof water particles, and they appear with suflicient persistence so that theyare plainly visible. The water itself forms both the plunger for raising and lowering'the pressure, and also one of the'plates between which the electrostatic field is formed, and also serves as a source 'ofwater vapor.

For demonstration, purposes I may provide a foot-switch for automatically controlling both theli ht and the electrostatic field circuits. Also, I may project the paths of the particles on ascreen, as is well understood by those skilled in the art. 7

Now"in"order to'acquaint those skilled in the art with the manner of constructing and operating a device according to my invention, I shall describe in connection with the accompanying drawings a specific embodiment of the same. I

In the drawings: 7

Figure 1 is a vertical sectional View through a device embodying my invention;

Fig. '2 is a horizontal section taken on the ing the space within the bottle; and

'Fig. ,3 is a longitudinal section of the aluminum plug which contains the source of. alpha rays or particles. I i I I I'proizide a glass bottle 1 ,which'is'pretterably made of pyreX glass, having a subirregular line 2-2 of Fig. l'and' showing also the PIOJGCtOl and screen for illuminatstantially' flat bottom Q a'nd a fairly" short body 3. i The body 3'has' a relatively long neck 4, the end of which is reduced at'5 to receive the co-operating neck 6 of a rubber bulb 7 ,'this bulb being-of elastic rubber such as isernployed for the bulb of a syringe. f On the inside oii' the bottom 2 I have'pr0- vided a metallic ring 8 which forms an electrode, this beingpreferably a platinum wire I thering electrode Sand simply depend upon which should be, for my purposes, between 100 and 200 volts direct current. The opposite plate is formed by abody of acidulated water 13, which fills the b'ulb"7,the neckt, and the body. 3 of the bottleyup to within a short clistance of the bottom 2.

" electrostatic field iris formed between the .electrodesjS and 13. Thebody 'ofwvat-er-ls V is connected through a wire "tothe external binding post '16, "which in turn 'is"con- T nfected't'o "t-heoppo'site pole of the battery'IQ.

I haved'iscovered that'the pola1'ityf'oftlie electrodes is iminateriahand that the; potential may remain Up Onthe fi'elCl constantly. 2O

he closed permanently or, if'desi'red ,it"may I provide, thereforefa switch 17' whichma'y that the observer when "he f approaches the apparatus, may close the foot switch to fthr'ow on the potential to form "an electrostatic field {in the space 'Hf'and also or trails appear within'the space 14, these closet'he electricj cir'cuit for the projector or other source of" illumination, as will bedeh a although, after" the-apparatus hasbeen in scribed later.

The liquid 13' is introduced into the bottle through a lateral c o'nnectionl8which'con- V tains a suitable valve 19forclosing'ofi'sueh connection. In the apparatuswhichl have employed, I have used' a' rubber tube and a pinchcock with a plainnipple'i'nstead oftlie 'valve'li).

Near the bottom' wall 2 and projecting from thesi'de'w'valls of the"b ottle-3;I provide 7 'a QIOtilid. and tapered seat which tlljie is placedan'aluminum plug" 21 'fittiii closely the ground tapered'seat and {held therein with stopcock grease ornie'rely' by "friction.

Thisplug 21, whichjis illustratedonan enlarged scale in 'Fig. 3, 'coinpri'sesfa hollow plug or'body 22, havingathin aluminum" window at its front end as indicated at'Q-3.

The rear end of 'the' body'22 is closed by a plug 24 'whichhas a wire stem'25 secured mounted, a small body 26-of' radioactive thereto. Upon the from end ofthis stem and closely adjacent the window 23, there is material; in this case radium bromide;

Inorder' to illuminate thespace 14,-1 pro vide a lantern or projector 27 'comprisi nga suitable source of'light281and condensing lens 29 for projecting a beam of light throughthe slit 30 of a screen 31,into said space 14: between'the electrodes 8 and 13.

In operation; the apparatus ismonnted; 1n

the position shown in Fig. 1,'andthe proector' 27 is arranged to throw a beam-of V flnoperation, theswitlil? is closed and the irrigate- 27 'is'excited to'throwlight into thespace'14 between the electrodes 8 and 1 3. Anelectrostatic'field is formed between these plates or electrodes 8 and 13 in said space 1 1 for-tl1e;purpose of sweeping out ions as fast as they are formed from any causewhatever.

The electrode 8 is preferably formed in the shape of a fine wire ring so as not to "obs'eure the visibility of the phenomena which occur in the space 1 f. The light is projected in from the side and the 0b- "s'erverstan'ds' With his eyeab'ove the apparatus and substantially normal to the flat vapor 'in the space 14 being compressed-at this time. "Then the pressureonthe bulb 7 is suddenly released to permit of 'a rapid Immediately a number of very fine streaks trails. proceeding mostly from the plug- '21,

use, it will be found that they appear to lead in every direction; thesetrails-"whenifthey first become visible appearing? as very-"faint "straightlines which rapidly enlarge and are warp d by the tubulence within said space 14: and disappear j u st"*as the*trail of'steam issuing from a "moving l'oeo'motive as viewed from 'a great distance.

The explanation of this phenomenon is "well known tothose)'ski l'le din the art.

It appears that particles of air andwater vapor," which "are "enc(ninteredby the particle in" its movement, become charged with posi- 'f tive electricity and serve, when the conditions arecorrect, as nuclei f-or'the formation of drops of water or'rarndrops and this sudden release ofv pressure "produces the i right conditions for such formation of droplets and particles'which aremov-ing at the time when the right conditions occur plainly leave 'their tra'ce or pathway marked with the condensing vaporwhich, under the effects of the light projected laterally into the space, are clearly Visible to theobserver. r.

Obviously'the bulb 7, or'equivalent means for moving the liquid piston "13' may be I Ur "transparent bottom wall'Qr'of the bottle or.

cylinder 3. "Thei plug 2l,"being in place so that-al ha particles are projected i-nto the electrostatic "afield," and the valve 19 5 being closed; the bulb 7 is grasped inthe hancl' and -compressed-fir 1y referee the liquid piston 13 uptowar dsthebottoinwall 2,the= air and placed 'at' a distance from the cylinder-or bottle 3, and this may be done so that'the mechanical effort of contacting'and expanding 'thebulb 7 may not be *directly tra'nsmitted' to' the bottle or cylinder 3.

' ItWiIlat once be apparent to those skilled in the art that modifications and changes may be made which, however, I "consider to come within the spirit and scope of 'theiin ventionas defined by the appended claims.

I claim:

1. In combination, a cylinder having a closed upper end wall, said end wall being transparent, a piston of conductive liquid in the lower part of said cylinder, said liquid leaving a space containing vapor, means for establishing an electrostatic field in said vapor, means for illuminating the space in which the electrostatic field is formed, and means for projecting alpha particles into the electrostatic field.

2. In combination, a cylinder having a glass end wall, an electrode mounted on said glass end wall, a piston of conductive water in the lower part of the cylinder, said water leaving a space containing water vapor, means for establishing an electrostatic field between said electrodes and the body of water, means for illuminating the space in which the electrostatic field is formed, and means for projecting alpha particles into the electrostatic field.

3. In combination, a cylinder having a closed upper end wall which end wall is transparent, a piston of conductive liquid in the lower part of the cylinder, said liquid leaving a space between it and the end wall, which space contains a vapor of said liquid, means for establishing an electrostatic field in said vapor, means for projecting alpha particles into the electrostatic field, and means for operating said liquid piston to raise and lower the fluid pressure on said vapor.

4. In combination, a closed inverted bottle having a transparent bottom wall and having a bulb connected to the neck of the same, a body of conductive water in said bottle filling the same to a point adjacent said bottom wall, means for establishing an electrostatic field in the space between said bottom wall and said body of Water, and

means for projecting alpha particles into the said space.

5. In combination, a closed inverted glass bottle having a rubber bulb connected to the neck of the same, an electrode lying against the bottom wall of the bottle, a body of conductive water in the bottle filling the same to a point adjacent the bottom wall and leaving a space charged with water vapor, a source of potential connected to said electrode and said body of water, said source of potential forming an electrostatic field between said electrode and the body of water, and means for projecting alpha particles into the space in which said electrostatic field is formed.

6. In combination, a glass bottle having a substantially flat bottom uppermost and having a rubber bulb connected to the neck of the same, an electrode disposed on the inside of the bottom wall, an opening in having a substantially flat bottom wall, an

electrode mounted on the inside of the bottom Wall, a conical seat formed about an opening in the side wall of the bottle adjacent the bottom wall, a plug in said seat, said plug having a source of alpha particles, a body of liquid substantially fillingthe bottle to leave a small space between the liquid and the electrode, a terminal connected to the electrode, a terminal connected to the liquid and means connected to the bottle for raising and lowering the liquid to raise and lower the pressure in said space between the liquid and the electrode.

8. The method of making visible the paths of alpha particles which comprises establishing an electrostatic field, confining a body of vapor in said field, compressing the body of vapor, projecting alpha particles. into the body of vapor and into the electrostatic field, and suddenly expanding the body of vapor while said alpha particles are being projected. v

9. The method of making visible the paths of alpha particles which comprises forming an electrostatic field, confining a body of vapor in saidfield, compressing the vapor, and contracting the field, expanding the field and reducing the vapor pressure, and projecting alpha particles through the body of vapor during the expansion thereof.

10. The method of making visible the I paths of alpha particles which comprises maintaining an electrostatic field, confining a body of vapor in said'field, compressing said vapor in said field, rapidly expanding said vapor, and during said compression and expansion continuously projecting alpha particles into said body of vapor in said field.

11. The method of making visible the paths of alpha particles which comprises establishing an electrostatic field, confining a body of vapor in said field, then simultaneously contracting the field and compressing the vapor, then simultaneously expanding the field and expanding the vapor, and projecting continuously alpha particles into said vapor during expansion.

In witness whereof, I hereunto subscribe my name this 16th day of December,-1924..

CHARLES T. KNIPP. 

